Buffering device

ABSTRACT

A buffering device for protecting a body, comprising an impactreceiving plate carrying a hollow resilient cylindrical buffering member, a core shaft coaxially secured to the impact-receiving plate, an intermediate hollow shaft extending from the body into the space between the buffering member and the core shaft, and an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill the space therebetween. The opposite end of the buffering member to the shock-receiving plate is secured to the intermediate shaft.

United States Patent [191 Nakamura et al.

[ 1 June 25, 1974 BUFFERING DEVICE Inventors: Kihei Nakamura, Yokohama;

Harumichi Yamazaki; Yoshikazu Kondo, both of Tokyo, all of JapanBridgestone Tire Company Limited, Tokyo, Japan Filed: Nov. 15, 1972Appl. No.: 306,835

Assignee:

Foreign Application Priority Data Nov. 17, 1971 Japan 46-91466 3,412,99011/1968 Gladstone ..267/35 Primary Examiner-James B. Marbert Attorney,Agent, or Firm-Fleit, Gipple & Jacobson hollow shaft extending from thebody into the space U.S. Cl. 267/139, 267/35 Int. Cl F16f 7/12 Field ofSearch 267/35, 33, 63 A, 139,

References Cited UNITED STATES PATENTS 10/1954 Dentler 267/63 A betweenthe buffering member and the core shaft, and an elastomeric fillersecured to the core shaft and the intermediate shaft so as to fill thespace therebetween. The opposite end of the buffering member to theshock-receiving plate is secured to the intermediate shaft.

5 Claims, 3 Drawing Figures PATENIEDJUN25I974 3.819.167

SHEET 2 BF 3 Load F lexure BUFFERING DEVICE BACKGROUND OF THEINVENTION 1. Field of the Invention:

This invention relates to a buffering device, and more particularly to abuffering device which is suitable for use in an automobile, a ship, ora machine for protection thereof by absorbing impact load thereto, suchas collision impact.

2. Description of the Prior Art:

There are a variety of buffering devices which use resilient rubber ormetallic springs. Most of the conventional buffering devices, however,absorb only a comparatively small amount of impact energy, and if onetries to absorb a large amount of impact energy with a buffering deviceof conventional structure, the buffering device becomes bulky. It isdifficult to install a bulky buffering device in a limited space, suchas in an automobile.

Conventional buffering device also has a shortcoming in that the amountof energy absorbed thereby heavily depends on the angle at which animpact is applied to the buffering device. More particularly, if theimpact is applied to a conventional buffering device in a directionwhich is greatly deviated from a direction of compressive axis of thedevice, or if the impact is a concentrated load which is applied to thebuffering device at a point greatly offset from the compressive axisthereof, the amount of the impact energy absorbed by the bufferingdevice is drastically reduced.

Therefore, an object of the present invention is to obviate theaforesaid difficulties of the conventional buffering devices byproviding an improved bufiering device.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a buffering device, which comprises a cylindrical bufferingmember having one end secured to an impactreceiving plate, anintermediate shaft having one end secured to a body to be protected, thefree end of the buffering member being coaxially secured to the outerperipheral surface of the intermediate shaft, a core shaft coaxiallyextending through the inside of the intermediate shaft and having oneend thereof secured to the impact-receiving plate, and an elastomericfiller secured to the core shaft and the intermediate shaft so as tofill a space therebetween. Whereby, impact energy applied to theimpact-receiving plate is absorbed in a dual fashion, i.e., at theinside and the outside of the intermediate shaft.

The buffering device of the aforesaid structure according to the presentinvention has two impactabsorbing elements; namely, an inner elementformed by the core shaft connected to the impact-receiving plate and theintermediate shaft connected to the body being protected with theelastomeric tiller connecting the two shafts, and an outer elementformed by the cylindrical buffering member having one end connectedtothe impact-receiving plate and the opposite end connected to thepheripheral surface of the intermediate shaft.

With the aforesaid structure according to the present invention, thecompressive axis of the buffering device, along which the bufferingdevice contracts upon application of an impact to the body at theimpact-receiving plate, apparently coincides with the common axis of thecoaxial core shaft, intermediate shaft, and buffering member. The use ofthe aforesaid two impactabsorbing elements ensures a high energyabsorption by the buffering device, even when the impact is applied tothe impact-receiving plate in an angular relation to the aforesaidcompressive axis or when an impact is applied to the impact-receivingplate at a position which is offset from the compressive axis by acomparatively large distance.

In a preferred embodiment of the present invention, the buffering memberis made of a hollow rubber-like resilient cylinder having acomparatively large impact energy absorbing capacity, so that the coreshaft and the intermediate shaft may fit in the hollow space of thebuffering member in a coaxial fashion. The elastomeric filler forconnecting the core shaft to the intermediate shaft is preferably madeof high-grade rubber, for instance, it is made of soft rubber having anelongation of not smaller than 500 percent at breakdown.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention, reference is made to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of a buffering deviceaccording to the present invention;

FIG. 2 is a graph showing the load-flexure characteristics of thebuffering device of FIG. 1; and

FIG. 3 is a schematic longitudinal sectional view of another bufferingdevice according to the present invention.

Like parts are designated by like numerals and symbols throughout thedifferent figures of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a hollowcylindrical buffering member 1, e.g., a resilient rubber cylinder with ahard ness of 40 to 98 according to Japanese Industrial Standard (118) K6301, is secured to an impactreceiving plate 9, and a bush-typebuffering assembly 2 is coaxially disposed in the hollow space of thebuffering member 1. The common longitudinal central axis of thebuffering member 1 and the bush-type buffering as sembly 2 isrepresented by a line X-X in the figure. The bush-type bufferingassembly 2 includes a metallic core shaft or cylinder 3 with a circularor rectangular cross section and an outer shaft or cylinder 4 whichtelescopically receives the core cylinder 3 with a suitable spacingtherefrom. A resilient. filler 5, which is, for instance, made of softrubber having an elongation of not smaller than 500 percent at breakdownand a modulus of elasticity of 30 Kg/cm at 300 percent elongation, isfitted in the spacing between the core cylinder 3 and the outer cylinder4. The opposing surfaces of the filler 5 are fastly bonded to the innerperipheral surface of the outer cylinder 4 and the outer peripheralsurface of the core cylinder 3, respectively. One end of the corecylinder 3 is secured to the impact-receiving plate 9, and a long bolt 6extends from the opposite end of the core cylinder 3 to that end of theouter cylinder 4 which faces said opposite end of the core cylinder 3. Anut 7 threadedly engages the long bolt 6 at the outside of the outercylinder 4, relative to the core cylinder 3, so as to interconnect thetwo cylinders 3 and 4. Such interconnection by the long bolt 6 and thenut 7, however, is not essential to the buffering device of the presentinvention. For instance, the bolt 6 and the nut 7 may be dispensed with,if the tiller keeps the two cylinders 3 and 4 in proper alignment witheach other. The nut connected end of the outer cylinder 4 is secured toa body to be protected, such as an automobile chas- In the embodiment,as shown in FIG. 1, the outer cylinder 4 is of unitary construction.Alternately, it is possible to form the outer cylinder 4 with aplurality of separate elements, so as to guide the core cylinder 3 whileholding the tiller 5 against impact load applied thereto.

To operatively connect the cylindrical buffering member 1 to thebush-type buffering assembly 2, a connecting member or flange 8 issecured to the opposite end of the buffering member 1 to theimpact-receiving plate 9. The flange 8 is secured to the outer cylinder4 by a suitable means, e.g., by welding.

In operation, let is be assumed that a load F is applied to theimpact-receiving plate 9 in alignment with the longitudinal axis XX ofthe buffering device. As a result, the cylindrical buffering member 1 iscompressed,

because the impact-receiving plate 9 is forced toward the fixed flange8. If the outer diameter d of the buffering member 1 is represented by d2r and its inner diameter is represented by 2r the cross sectional areaS of the buffering member, which is taken at right angles to the axis XXand surrounded by the outer peripheral surface thereof, is given by S 1'n-r and the similar cross sectional area of the hollow space S of thebuffering member is given by S 111 If a ratio of the outer diameter d ofthe buffering member 1 to its height h, taken in parallel to the axisXX, is kept constant, the amount of energy to be absorbed by thebuffering member 1 in response to its compression depends on the ratioof the aforesaid two areas, namely 8 /8 The ratio of h/d of thebuffering member 1 is preferably 0.8 to 1.7, but the invention is notrestricted by such range of the h/d ratio.

FIG. 2 shows load-flexure characteristics of the buffering device of thepresent invention, as shown in FIG. 1. In the figure, the curve arepresents such characteristics for the buffering member 1 alone, forthe case of a medium S /S ratio of about 1.4 to about 4.0. The curve arepresents the similar characteristics for the case of a comparativelylarge S /S ratio of about 4.0 or larger, while the curve a representsthe similar charac' teristics for the case of a comparatively small S 18ratio of about 1.4 or smaller.

The curve b of FIG. 2 shows the load-flexure characteristics of thetiller 5, in response to the movement of the core cylinder 3 relative tothe outer cylinder 4, in the direction of the axis XX. The relativemovement of the cylinders 3 and 4 causes shearing stress in the tiller5, and the flexure of the curve b is due to such shearing stress. Withsuch flexure, the filler 5 also absorbs the impact energy.

In the buffering device according to the present invention, thebuffering member 1 and the bush-type buffering assembly 2 are disposedin a coaxial fashion about the longitudinal axis XX, so that the impactload F applied to the impact-receiving plate 9 is simultaneously borneby both the buffering member 1 and the bush-type buffering assembly 2.Thus, the overall load-flexure characteristics of the buffering devicebecomes the sum of that of the member I and that of the assembly 2, asshown by the curves c c, and c of FIG. 2.

More particularly, if the buffering member 1 has a comparatively smallS,/S ratio of about 1.4 or smaller resulting in the load-flexurecharacteristics of the curve a of FIG. 2, the overall load-flexurecharacteristics of the buffering device according to the presentinvention is given by the summation of that of the curve a and that ofthe curve b for the tiller 5, as shown by the curve 0 If the 8 /8 ratioof the buffering member 1 is about 1.4 to 4.0, the overall load-flexurecharacteristics of the buffering device becomes as shown by the curve 0.Similarly, for a large S /S ratio in excess of about 4.0, the overallload-flexure characteristics of the buffering device becomes as shown bythe curve c of FIG. 2. Thus, a desired load-flexure characteristics canbe selected from the curves of FIG. 2, by properly selecting a suitableconfiguration of the buffering member 1 and the bush-type bufferingassembly 2.

The inventors have found out that the desired loadflexurecharacteristics can be achieved with a smaller buffering deviceaccording to the present invention, as compared with conventionalbuffering devices. The amount of the impact energy to be absorbed by thebuffering device depends on the aforesaid load-flexure characteristics.Thus, with the present invention, a desired impact energy absorption canbe achieved with a device of smaller size than that of conventionalbuffering devices.

In the buffering device of the present invention, as shown in FIG. 1, ifan impact load F is applied at an angular relation to the longitudinalaxis XX, or if a concentrated load F" is applied to the impact-receivingplate 9 at a point offset from the axis XX, the core cylinder 3 which issurrounded by the resilient filler 5 resists against any swaying of theimpact-receiving plate 9 relative to the axis X-X. Whereby, thebuffering device of the present invention ensures a high energyabsorption for the angularly applied impact load and the offset impactload.

The long bolt 6 carrying the nut 7 acts to guide the displacement of theinner cylinder 3 along the axis XX. In addition to such guiding, theinitial loading to the buffering member 1 and the tiller 5 can beadjusted by turning the nut 7 so as to regulate the position of theimpact-receiving plate 9 relative to the body 10 being protected.Whereby, the load-flexure characteristics and the energy absorption bythe buffering device can be controlled at will.

FIG. 3 illustrates another embodiment of the present invention. If aconcentrated impact load F" is applied to an impact-receiving plate 9 ata position which is off set from a longitudinal axis X-X of thebuffering device, a bufi'ering member 1 may tend to sway relative to theaxis XX, especially when the buffering member 1 has a comparatively lowrigidity in the lateral direction as shown by the arrow P. When thebuffering member 1 is swayed, the desired load-flexure characteristicsand impact absorption, as shown by the curves c, 0 and 0 cannot beachieved. In the embodiment of FIG. 3, two guide pieces 11 and 12 areused to guide the movement of a core cylinder 3 relative to an outercylinder 4 along the axis X--X. Whereby, the core cylinder 3 and theimpact-receiving plate 9 are prevented from the swaying, and the desiredcompression of the buffering member I and the shearing stress of thefiller 5 can be ensured.

The guide pieces 11 and 12, in effect, improve the lateral rigidity ofthe buffering device, by preventing the impact-receiving plate 9 fromswaying relative to the axis X-X. The guide piece 11 is secured to theopposite end of the core cylinder 3 to the impactreceiving plate 9, soas to keep a clearance 11a between the inner peripheral surface of theouter cylinder 4 and the outer peripheral edge of the guide piece 11.The other guide piece 12 has a central hole 12a and is secured to theopposite end of the outer cylinder 4 to a body being protected, whileallowing the core cylinder 3 to move through the central hole 12a.

It is, of course, possible to use only one of such guide pieces, i.e.,11 or 12.

As described in the foregoing disclosure, with the structure accordingto the present invention, a large impact energy absorption can beobtained by a comparatively small buffering device, and the desiredenergy absorption can be ensured even for angularly applied impact loadand concentrated offset load.

We claim:

1. A buffering device comprising a buffering member having one endsecured to an impact-receiving plate, an intermediate shaft having oneend secured to a body to be protected, the free end of the bufferingmember being coaxially secured to the outer peripheral surface of theintermediate shaft, 21 core shaft coaxially extending through the insideof the intermediate shaft and having one end thereof secured to theimpact-receiving plate, an elastomeric filler secured to the core shaftand the intermediate shaft so as to fill a space therebetween, and guidemeans connected between the end of the core shaft remote from saidimpact-receiving plate and the body to be protected, for maintaining asubstantially coaxial relationship between said intermediate shaft andsaid core shaft during impact.

2. A buffering device according to claim 1 wherein said guide meanscomprises a guide bolt secured to the end of the core shaft oppositefrom said impactreceiving plate so as to extend into said body throughone end of said intermediate shaft, and a nut threadedly engaging saidbolt at the outside of said intermediate shaft, whereby the initialrelation between said core shaft and said intermediate shaft iscontrolled by adjusting said nut relative to said bolt.

3. A buffering device according to claim 1 and further comprising aguide piece secured to the end of the core shaft opposite from saidimpact-receiving plate so as to maintain a small clearance from theinner peripheral surface of said intermediate shaft to said core shaftfor guiding the movement of the core shaft relative to the intermediateshaft.

4. A buffering device according to claim 1 and further comprising aguide piece secured to the end of said intermediate shaft opposite fromsaid body, said guide piece having a central hole through which saidcore shaft moves under guidance of the guide piece.

5. A buffering device according to claim 3 and further comprising asecond guide piece secured to the end of said intermediate shaftopposite from said body, said second guide piece having a central holethrough which said core shaft moves under guidance of said second guidepiece.

1. A buffering device comprising a buffering member having one end secured to an impact-receiving plate, an intermediate shaft having one end secured to a body to be protected, the free end of the buffering member being coaxially secured to the outer peripheral surface of the intermediate shaft, a core shaft coaxially extending through the inside of the intermediate shaft and having one end thereof secured to the impact-receiving plate, an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill a space therebetween, and guide means connected between the end of the core shaft remote from said impact-receiving plate and the body to be protected, for maintaining a substantially coaxial relationship between said intermediate shaft and said core shaft during impact.
 2. A buffering device according to claim 1 wherein said guide means comprises a guide bolt secured to the end of the core shaft opposite from said impact-receiving plate so as to extend into said body through one end of said intermediate shaft, and a nut threadedly engaging said bolt at the outside of said intermediate shaft, whereby the initial relation between said core shaft and said intermediate shaft is controlled by adjusting said nut relative to said bolt.
 3. A buffering device according to claim 1 and further comprising a guide piece secured to the end of the core shaft opposite from said impact-receiving plate so as to maintain a small clearance from the inner peripheral surface of said intermediate shaft to said core shaft for guiding the movement of the core shaft relative to the intermediate shaft.
 4. A buffering device according to claim 1 and further comprising a guide piece secured to the end of said intermediate shaft opposite from said body, said guide piece having a central hole through which said core shaft moves under guidance of the guide piece.
 5. A buffering device according to claim 3 and further comprising a second guide piece secured to the end of said intermediate shaft opposite from said body, said second guide piece having a central hole through which said core shaft moves under guidance of said second guide piece. 